1. Field of the Invention
The present invention relates to a pattern forming method which is used for a process for manufacturing a semiconductor such as an integrated circuit (IC), the manufacture of a circuit board for a liquid crystal, a thermal head, or the like, and other lithographic processes for photofabrication, as well as a composition for forming a protective film which is suitably used in the pattern forming method, a method for manufacturing an electronic device, and an electronic device. The present invention relates to a pattern forming method which is suitable for, in particular, performing exposure with a liquid immersion type projection exposure device, as well as a composition for forming a protective film which is used for the pattern forming method, a method for manufacturing an electronic device, and an electronic device.
2. Description of the Related Art
Since a resist for a KrF excimer laser (248 nm) was developed, an image forming referred to as chemical amplification as an image forming method of a resist has been used in order to compensate for desensitization caused by light absorption. By using an example of an image forming method with positive type chemical amplification, the method is an image forming method in which an acid generator included in an exposed area decomposes upon exposure to generate an acid; in a post exposure bake (PEB), an alkali-insoluble group is changed into an alkali-soluble group by using the generated acid as a reaction catalyst; and the exposed area is removed by alkali development.
On the other hand, not only a positive tone has been developed, but also a negative tone image forming method (hereinafter also referred to as a “NTI process” (also referred to as a negative tone imaging: NTI)) using a developer including an organic solvent (hereinafter also referred to as a “organic solvent developer”) has recently been developed (see, for example, JP2008-292975A and JP2011-141494A). For example, in JP2011-141494A, taking into consideration a demand for further improvement of line width roughness (LWR), depth of focus (DOF), and other various types of performance, each of which is presumed to be mainly caused by swelling during development, in pattern formation by alkali development using a negative type resist composition in the related art, a chemical amplification type resist composition, to which a specific compound including at least one of a fluorine atom or a silicon atom has been added, in a negative tone pattern forming method using a developer including an organic solvent.
Moreover, in order to make semiconductor elements finer, the wavelength of an exposure light source has been shortened and a projection lens with a high numerical aperture (high NA) has been advanced. Thus, an exposure machine using an ArF excimer laser having a wavelength of 193 nm as a light source has been currently developed. In addition, as a technique for further improving resolving power, a so-called liquid immersion method in which a liquid having a high refractive index (hereinafter also referred to as an “immersion liquid”) is filled between a projection lens and a sample has been proposed from the related art.
It is pointed out that in a case where a chemical amplification resist is applied to liquid immersion exposure, a resist layer is brought into contact with an immersion liquid during exposure, and therefore, the resist layer is modified or components adversely affecting the immersion liquid are exudated from the resist layer. In WO04-068242A, an example in which resist performance changes by immersing a resist for ArF exposure in water before and after the exposure is described, and points out the example as a problem in liquid immersion exposure.
As a solution for avoiding such a problem, a method in which a protective film (hereinafter also referred to as a “topcoat”) is provided between a resist and a lens to prevent the resist and water from being into direct contact with each other (see, for example, WO04-074937A, WO05-019937A, and JP2005-109146A).
In an NTI process in which excessive generation of an acid in the resist surface layer by the decomposition of an acid generator upon exposure causes an excessive deprotection reaction of an acid-decomposable group in the surface layer occurs, and thus, an exposed area remains as a pattern after development, the pattern is easily in a T-top shape. In a case where the pattern is in the T-top shape, for example, then performance such as depth of focus (DOF) and exposure latitude (EL) is deteriorated. As a result, for example, JP2013-61647A and JP2013-61648A disclose a technique in which a basic quencher is added to a topcoat layer that covers a resist film for the purpose of neutralizing an excessive acid generated in the resist surface.